This was such an interesting question and it sent me down a WORMHOLE of trying to find out the exact reason. I had a feeling I knew but I wanted to make sure that I was giving y'all the right info.
First of all, the tradition of stamping your name as a μΈκ°λμ₯ (identity stamp) came from China a very long time ago! In China, the color red is seen as representing prosperity and happiness! This is why people stamp their official seals in red because we usually use them for contracts or important things π
Writing your name in red, however, is a superstition that has been around for a while and has three possible origins. The superstition is that if you write your name in red, then you will die. These are the three origins:
1. It looks like blood (the red color) π΄
2. There is a story that a long time ago, there was an emporer who liked writing his name in red because it was an auspicious color - but if commoners did it he would have them killed πͺ
3. The names of the dead during the Korean War were marked in red ποΈ
Hope this helps!!!! | 
